[Stoves] Frame stoves and biomass boxes.......was...Re: cookstoves for Cameroon

[Crispin Pemberton-Pigott]

Dear Anh

 

I want to compliment you on this brilliant approach to cooking and making char at the same time. This type of co-firing is used in sawdust stoves, and to a certain extent Cecil reports the use of co-firing different moisture content fuels in Indonesia in order to get particular control over the fire.

 

I think AD Karve will be interested to try this on a small scale as a way to make the char the feeds into the ‘elbow macaroni’ fuel used in Sarai stoves.

 

If it is not obvious to readers, the idea is to load fuels that will not burn effectively on their own (sawdust stove, leaf stove etc) into a container that is roasted by the wood fire. The rubbish fuels are then gasified and that gas adds to the general combustion. It is likely to lower emissions of PM (a lot) because of the high hydrogen content in the gas.

 

Congratulations

Crispin

 

 

 

Dear Paul,

 

"Frame" is just a translation from Vietnamese name used for the extra metal frame to support large pots (>50 litters). With that metal frame, we can take the stove out, add more fuel without moving the heavy pot which stay on the metal frame.

 

 

The biomass box can be in various side and shape, can be just a metal tube (our first tests). We need to seal the bottom of the box to prevent biomass falling out and air getting in. The top of the box can be open but I prefer to have cap with some small holes (3-4 holes at 1cm diameter), with that we can reduce air getting in (to keep the biochar from burning out) and concentrate the gas output and make a longer flame from the holes. 

 

The box side: can be same height with the combustion chamber, the width can be ~ 1/3 of the combustion chamber, so with 2 boxes you can replace ~60% wood with small biomass (burning time will reduce but you can add more wood/main fuel later to extend cook time) 

 

For small tube type box, you can put in as if it is a wood stick. I prefer the square shape box to put on the sides of the square stove, it will only use waste heat that transfer out sideway to heat the biomass inside, it also reduce temperature of the stove's side cover a bit. 

 

Duration of the box varies depending on biomass type, saw dust is the best, can burn for 15-20 min more (after fire from main wood burnt out).  

 

Limitations: 

- it's hard to replace biomass box when it burnt out, need extra tool to replace the box when stove is burning hot. 

- some biomass burn out too fast: straw, garden leaves,... so cannot use with too small boxes

 

Here are some picture of the boxes before and after cooking.

 



 

Anh

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